The present invention relates to a machine for blow-moulding plastic containers, provided with a motor device and two in-line connecting rods for opening/closing the mould.
It is known in the technical sector relating to the packaging of liquid products and the like that there exists the need to produce containers made of plastic suitable for this purpose.
It is also known that said containers are formed in suitable blow-moulding machines provided with associated moulds (composed of two half-moulds movable so as to open/close) into which a tube made of plastic extruded upstream of the mould is introduced and blow-moulded.
Also known are machines for moulding plastic containers comprising a unit for extruding plastic tubes, a blow-moulding unit and a mould for containing the containers which is formed by two half-moulds movable, upon operation of associated first means, in a longitudinal direction and symmetrically with respect to a fixed axis perpendicular to said longitudinal direction, the entire unit formed by the mould and the associated first operating means being movable, upon operation of associated second operating means, in a transverse direction from a first position, corresponding to positioning of the mould below the extrusion unit, to a second position corresponding to positioning of the mould below the blow-moulding unit, and vice versa, the first means for opening/closing the two half-moulds comprising at least one oil-hydraulic cylinder arranged parallel to the longitudinal axis and integral with a plate displaceable with a translatory movement.
Although fulfilling their function, these machines nevertheless have certain drawbacks essentially arising from the need to provide pipes for supplying the oil to the cylinder for operating the moulds, resulting in the possibility of leakages or contamination affecting the environment surrounding the machine.
IT 1,326,664 in the name of the same present applicants also discloses a machine in which said first means for operating the half-moulds are of the electrical type; this solution, however, proves to be particularly complicated owing to the large number of mechanical parts for the transmission of the reverse movement to the two half-moulds, which may give rise to play and therefore lack of precision in the closing symmetry of the two half-moulds.
In addition to this, the mechanical transmissions of conventional machines are the cause of vibrations which do not allow precise centering of the seats of the mould with the blowing-moulding injectors, particularly in the case of multiple heads where centering is correct only for some of them, while the remaining heads are off-centre with respect to the corresponding injector, resulting in a large number of production rejects.